As an officer and long time member of the guild, I manage alot of the gbank transactions. I'm curious as to how most guilds maintain their gbanks. Every so often I will go in and clear out some old mats or gear and sell them, placing the gold back in the bank. I will distribute among regular guildies any excessive pots, scrolls, flasks and food etc. We use our gold for guild events and sometimes to help out a guild tank that has been doing alot of runs for the guild.
I try to deter folks from putting old mats in the gbank as they just take up too much room. It is absolutely much easier to organize the glyphs now with the colours and patterns for classes. It was a nightmare for a while.
I was just reading a post about a guild that has one tab as a free for all for guildies which I think is a great idea. Placing things that have been in the guild bank for a while or just old stuff. Putting a limit of 3 items per day to be removed. It can be hard to keep the balance of items at times and having a free for all tab may help.
Perhaps it's just our guild but it seems people hate to ask for anything from the gbank hehehe. When gbanks started I was thinking there were going to be issues with some people trying to take advantage etc, but its been the opposite. People hate to ask and hate to take stuff. Hopefully with a free tab guildies will be more likely to dip in.